What does it mean?
B1731 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Seat Driver Rear Down Switch Circuit Short to Battery .
Symptoms
- Rear of the seat cushion drops by itself or refuses to lower
- Seat tilt cannot be adjusted while slide and recline still respond
- Motor runs to the bottom stop and stalls, sometimes with an audible click from the module
- Memory positions fail to recall because one axis never reaches target
- Code resets as soon as it is cleared, often while the seat is being operated
Likely causes
- Spilled liquid or debris inside the switch pack bridging the rear-down contact to the supply
- Worn or stuck rocker contact that stays closed after use
- Rear-down signal wire chafed where the loom passes the seat rail or a sharp frame edge
- Water-damaged under-seat connector with corrosion between terminals
- Aftermarket wiring spliced into the seat loom and feeding voltage into the input
- Seat control or memory module output stage failure
How to fix it
- Read codes and watch the rear-down input live with the switch untouched
- Wiggle the seat loom through the full range of travel while monitoring the input state
- Unplug the switch pack; a normal reading afterwards points at the switch
- Measure the signal wire for battery voltage with the switch disconnected to confirm the short
- Inspect the loom at the rail, cushion frame and under-seat connector for chafe, crushing and corrosion
- Clean or replace the switch pack and repair damaged wiring with a sealed, insulated joint
- Replace the seat module last, after the switch and harness have been proven good